Numerical control system

ABSTRACT

A numerical control system in which data signals are exchanged between a computer processing device MPU and each function block through an address bus ABUS and a data bus DBUS. Parallel electric signals are converted into serial signals by shift registers SHR 1  and SHR 2 , and are converted into light signals by transmitters Tx 11  and Tx 12 . The light signals are delivered to pulse distributors PDN through optical fiber cables OF 1  and OF 2  and these light signals are converted back to electric signals by receivers Rx 3  and Rx 4  and are further converted into parallel signals by shift registers SHR 3  and SHR 4 . The parallel signals are delivered to a pulse distributor PD as position signals in the directions of X, Y and Z axes thereby to driving servomotors.

This is a continuation of co-pending application Ser. No. 413,335 filedon Aug. 23, 1982.

BACKGROUND OF THE INVENTION

The present invention relates to a numerical control system forcontrolling various machines such as wire-cut electrospark machine,turret punch press, composite machine tool and so forth and, moreparticularly, to a numerical control system in which various functionsare coupled by means of optical fibers.

Most current numerical control systems (referred to as "NC system",hereinafter) incorporate computers. More specifically, these NC systemshave the following constituent elements: a processing device such as amicroprocessor adapted to perform various processings such as numericalcontrol processing, edit processing, transmission and receiving of dataand so forth, in accordance with a control program and a machiningprogram; memories such as a nonvolatile data memory, a working memoryand a control program memory; a paper tape reader and a paper tapepuncher; a control panel incorporating a display device; an externalstorage medium such as cassette type magnetic tape; and a heavy currentcircuit for signal exchange between the controller and the machine, e.g.delivery of signals, such as a miscellaneous function command or aspindle rotation command, to the machine and delivery of work completionsignals to the controller upon confirming the completion of the work inresponse to the miscellaneous function command or the spindle rotationcommand. The NC system further includes servomotor units having drivingmotors for positioning the spindle in the directions of X,Y and Z axes,and a pulse distributor for distributing pulses to these servo units.

In these known NC systems, the exchange of data between differentfunctional blocks (for example, paper tape reader and microprocessor) inthe system is made through a data bus, while the delivery of the addressis made through an address bus. As a matter of fact, in order toconcurrently send signals comprising n bits constituting each unit ofdata, each data bus includes n lines, so that the connection of buslines between associated functional blocks is very complicated. Inaddition, since the NC systems are usually used in factories or the likewhere there is a lot of electrical noise, the address bus often and thedata bus tend to pick up the electrical noise resulting in a malfunctionof the NC system. Another problem of the prior art is that a specificconsideration or measure is required to standarize the interface betweenassociated functional blocks which raises the cost of the NC system.

SUMMARY OF THE INVENTION

In order to obviate these problems of the prior art, according to theinvention, there is provided a numerical control system in which thedata processing section is connected to various functional blocks bymeans of buses comprising optical fibers, and the data is transmitted inthe form of serial light signals through these data buses comprising theoptical fibers. More specifically, each functional block is providedwith a shift register for converting parallel signals into serialsignals, a transmitter converting the output signal from the shiftregister into a light signal and to transmitting the light signal to theoptical bus through a photo branching device, a receiver for convertingthe light signal coming from the photo branching device into an electricsignal, and a shift register for converting the serial output from thereceiver into a parallel signal. Thus, according to the invention, thedata processing section and each functional block are connected by adata bus comprising an optical fiber cable and the exchange of the databetween the data processing section and each functional block is madethrough this data bus comprising by the optical fiber.

Thus, the present invention provides a compact NC system which canperfectly eliminate the pick up of electrical noise by the bus lines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram of a conventional NC system;

FIG. 2 is a circuit block diagram of an NC system constructed inaccordance with an embodiment of the invention;

FIG. 3 is a circuit block diagram of a tape reader; and

FIG. 4 is a circuit block diagram of a heavy current circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention will be described in more detail hereinafter withreference to the accompanying drawings in comparison with the prior art.

FIG. 1 is a schematic circuit block diagram of a conventional NC systemincorporating a computer. In the drawings, a symbol MPU represents aprocessing unit such as a microprocessor, adapted to perform variousprocessings such as numerical control processing, edit processing,transmission and receiving of signals and so forth, in accordance with acontrol program and a processing program. A nonvolatile data memory DMis adapted to store various processing data for controlling a machinetool. A working memory WM is composed a volatile random access memoryhaving a high speed and a small capacity and is adapted to temporarilystore the machining data read out from the data memory DM. A controlprogram memory PM is adapted to store the control program, whle a pulsedistributor PD performs a known pulse distribution operation todistribute pulses Xp,Yp and Zp upon receipt of position commands X,Y andZ.

Servo control circuits SVX,SVY and SVZ produce, upon receipt of thedistribution pulses Xp,Yp and Zp, as well as feedback pulses Xf,Yf andZf which are produced each time the rotation of the driving motorsreachs a predetermined value, analog voltages proportional to |Xp-Xf|,|Yp-Yf| and |Zp-Zf|. The driving motors for driving the spindle in thedirections of X,Y and Z axes are represented by DMX,DMY, and DMZ,respectively. Pulse coders PCX,PCY and PCZ attached to the shafts of thedriving motors DMX,DMY and DMZ produce the aforementioned feedbackpulses Xf,Yf and Zf each time the rotation of the motor shafts reaches apredetermined value. The servo control circuits SVX,SVY and SVZ, D.C.motors DMX,DMY and DMZ and the pulse codes PCX,PCY and PCZ incombination constitute respective servo units which perform servocontrol to nullify the voltages |Xp-Xf|,|Yp-Yf| and |Zp-Zf|,respectively. A paper tape reader PTR is adapted to read numericalcontrol information (machining data) punched in a paper tape and tostore the same in the data memory DM. A paper tape puncher PTP isadapted to punch a paper tape in accordance with the machining datastored in the data memory DM, thereby storing the machining data in thepaper tape which is an external storage medium. A symbol MDI representsan operation panel which incorporates a display device, while a symbolEM represents an external memory medium such as a cassette type magnetictape or a cassette type magnetic bubble memory. A symbol PC represents aheavy current circuit through which signals are exchanged between the NCsystem and a machine tool MAC. Namely, the heavy current circuit PCdelivers to the machine tool MAC a signal DON representing amiscellaneous function (M function) and a spindle rotation function (Sfunction) as a contact signal, and, as the machine tool accomplishes theoperation in response to the miscellaneous function command or thespindle rotation command, the heavy current circuit produces acompletion signal DIN. Address buses for transferring the addresssignals and the data buses for transferring various data are representedby ABUS and DBUS, respectively.

In the conventional NC system explained above, the exchange of databetween associated functional blocks is made through the data bus DBUS,while the exchange of the address signals is made through the addressbus ABUS. Actually, however, each bus consists of n lines in order toconcurrently transmit the signals of n bits constituting each unit ofdata. In consequence, the wiring of bus lines is very complicated.

These problems, however, are completely overcome by the presentinvention.

FIG. 2 shows a circuit block diagram of an NC system constructed inaccordance with an embodiment of the invention, in which the samereference symbols are used to represent the same parts as those in theconventional system explained before.

Referring to FIG. 2, a reference numeral 1 denotes a data processingsection which includes, as in the case of the data processing section ofthe conventional system, a processing unit MPU, control program memoryPM, data memory DM and working memory WM. These functions are connectedthrough address bus ABUS and data bus DBUS of 8 or 16 bits. A shiftregister SHR₁ is adapted to convert the parallel address signal of (n+1)bits delivered through the address bus ABUS, i.e. signals b_(o) to b_(n)delivered parallelly at one time, into a serial bit signal starting fromthe bit b_(o) and ending in the bit b_(n). A transmitter Tx₁₁ representsa transmitter which converts the electric serial address signal comingfrom the shift register SHR₁ into a light signal and to transmits thethus obtained light signal. For instance, the transmitter Tx₁₁ comprisesan LED or a semiconductor laser. A symbol OF₁ represents an opticalfiber cable comprising the address bus. A shift register SHR₂ is adaptedto convert the parallel data signal of (n+1) bits coming through thedata bus DBUS, i.e. the signals b_(o) to b_(n) delivered concurrently,into a serial bit signal starting from b_(o) and ending in b_(n). Atransmitter Tx₁₂ is adapted to convert the electric serial bit signaldelivered by the shift register SHR₂ into a light signal. A symbol OF₂represents an optical fiber cable for the exchange of the data signals.A photo divider OD₁ is adapted to transmit the light signal deliveredthereto by the transmitter Tx₁₂ to the optical fiber cable OF₂ and totransmit the light signal delivered thereto by the optical fiber cableOF₂ to the receiver RX₂.

A symbol PDN represents a pulse distributor. The pulse distributor PDNincludes a photo branching device OB₁ which divides and receives thelight signal from the optical fiber cable OF₁ serving as the addressbus, and a photo branching device OB₂ adapted to divide and receive thelight signal from the optical fiber cable OF₂ serving as the data bus. Areceiver Rx₃ is adapted to receive the serial bit signal from the photobranching device OB₁ and to convert the same into an electric pulsesignal. A shift register SHR₃ converts the electric serial bit signaldelivered thereto by the receiver Rx₃ into a parallel bit signal. Adecoder DEC₁ decodes the address signal coming from the shift resistorSHR₃ and produces an enable signal. A receiver Rx₄ receives the serialbit light signal from the photo branching device OB₂ and converts thesame into an electric pulse signal. A reference symbol SHR₄ represents ashift register adapted to convert the electric serial bit signaldelivered thereto by the receiver Rx₄ into a parallel bit signal. Theshift register delivers to the pulse distributer the parallel datasignals representing the position commands in X,Y and Z directions.

In the NC system of the invention, the functional block which is adaptedonly to receive the data signal from the data processing section 1 butnot to transmit the data to the processing section 1, e.g. the tapepuncher, may be provided simply with a mechanism including photobranching devices disposed in the optical fiber cable OF₁ serving as theaddress bus and the optical fiber cable OF₂ serving as the data bus,receivers for receiving the signals from the photo branching devices andconverting the serial light signals into serial electric signals andshift registers for converting the serial electric signals into parallelelectric signals, as in the case of the pulse distributor.

FIG. 3 is a functional block diagram showing a tape reader which is oneof the functional blocks adapted to perform only the transmission of theread data in accordance with the instructions given by the dataprocessing section 1. Optical fiber cables OF₁ and OF₂ are provided withrespective photo branching devices OB. Symbols Tx and Rx representtransmitters and receivers, respectively. The photo branching devicesOB, transmitters Tx and the receivers Rx are materially identical tothose explained before, so that a detailed description thereof isomitted. A shift register SHR₅ is adapted to convert a serial signalinto a parallel signal, while another shift register SHR₆ is adapted toconvert the parallel signal into the serial signal. The arrangement issuch that the address signal which is a signal light signal derived fromthe optical fiber cable OF₁ is branched by the photo branching device OBand is converted into an electric signal by the receiver Rx. Theelectric signal is then changed by the shift register SHR₅ into aparallel address signal which in turn is delivered to the decoder DEC.On the other hand, the parallel electric signal read by the tape readeris converted by the shift register SHR₆ into a serial electric signalwhich in turn is converted into a light signal by the transmitter Tx.The light signal is then forwarded from the photo branching device OB tothe optical fiber cable OF₂ and is fed to the data processing section 1.In the NC control system of the invention, the functional block adaptedonly to send the data to the processing section 1 but not to receivedata from the processing unit 1, e.g. control panel, may simply beprovided with a transmitter for converting the electric signal intolight signal, as in the case of the paper tape reader.

FIG. 4 is a functional block diagram of a heavy current board which is afunctional block adapted to transmit and receive data in accordance withthe instructions given by the data processing section 1. The heavycurrent board includes a transmission device and a receiving deviceconnected between the heavy current circuit PC and the optical fibercable OF₂ serving as the data bus. The transmission device comprises thetransmitter Tx and a shift register SHR_(A) for converting the parallelsignal into a serial signal, while the receiving device comprises thereceiver Rx and a shift register SHR_(B) for converting the serialsignal into a parallel signal. The receiving device is adapted todeliver to the heavy current circuit PC various signals DON such as themiscellaneous function (M function) command, the spindle rotationfunction (S function) command and the tool selection function (Tfunction) command forwarded from the data processing section 1. Thetransmission device is adapted to receive, as the machine tool completesthe work in response to the command such as miscellaneous functioncommand, spindle rotation command and the tool exchange command, acompletion signal DIN from the heavy current circuit PC, and deliversthe same through the photo branching device OB to an optical fiber cableOF₂ functioning as the data bus.

This arrangement can be applied to other functional blocks whichperform, as in the case of the heavy current circuit mentioned above,both the transmission and reception of the data, e.g. a datatransmitter/receiver connected to a robot controller.

The NC system of the described embodiment have two independent buses:namely, a data bus and an address bus. Needless to say, however, thisarrangement is not exclusive and the arrangement may be modified to makecommon use of a single bus for both the data signal and address signal,in such a manner that, after delivering the address signal to the commonbus in a bit serial form, the data signal is transferred through thecommon bus. Such a modification reduces the number of the transmittersand receivers almost to a half of those in the conventional system.

As will be realized from the foregoing detailed description, accordingto the invention, it is possible to remarkably simplify the busarrangement as compared with the conventional system and to constructthe functional blocks in the form of modules, thanks to the use ofoptical fiber cables for the data transfer. In consequence, the size ofthe circuit of the central data processing section is made small enoughto permit the mounting of the central data processing section on a partof the machine tool in a compact manner, which in turn permits areduction of the size of the machine tool. The use of the optical fibercable permits a high speed data transfer, while eliminating theattenuation of the signal or the influence of noise which may be causedwhen the length of the bus is increased. The high speed data transfer onthe other hand makes it possible to transfer the data in the bit serialform without a substantial increase in the processing time as comparedwith the conventional system in which the data signals are transferredin a bit parallel manner through bus lines made of electric conductors.The use of the optical fiber cables does not raise the cost of the NCsystem substantially, since the number of elements necessary for theoptical fiber data transfer, e.g. transmitters, receivers, connectorsand so forth, is not so large because only one or two buses arenecessary. Furthermore, it is possible to standarize the interface byarranging the components such that various functional blocks in the NCsystem are coupled by a common bus. Thus, the present invention offersvarious advantages which could never be attained by the conventional NCsystems.

What is claimed is:
 1. A numerical control system for controlling amachine, comprising:a data processing section for processing datasignals; a bus comprising an optical fiber cable operatively connectedto said data processing section, said bus transferring therethrough thedata signals in the form of bit serial light signals; and functionalblock means, operatively connected to said bus, for controlling themachine in dependence upon the data signals from said data processingsection, comprising:a photo branching device operatively connected tosaid optical fiber cable; a receiver, operatively connected to saidphoto branching device, for converting the bit serial light signalsdelivered thereto by said photo branching device into a serial electricsignal; and a shift register, operatively connected to said receiver,for converting the serial electric signal delivered by said receiverinto a parallel electric signal.
 2. A numerical control system forcontrol of a machine, comprising:a data processing section forprocessing data signals; a bus comprising an optical fiber cable,operatively connected to said data processing section of said numericalcontrol system, for transferring therethrough the data signals in theform of bit serial light signals; and functional block means forcontrolling the machine in dependence upon the data signals from saiddata processing section, comprising:a first shift register forconverting a first parallel electric signal into a first serial electricsignal; a transmitter, operatively connected to said shaft register, forconverting the first serial electric signal coming from said shiftregister into a serial light signal; a photo branching device,operatively connected to said optical fiber cable and said transmitter,for transmitting the serial light signal to and from said bus throughsaid photo branching device; a receiver, operatively connected to saidphoto branching device, for converting the serial light signal derivedfrom said photo branching device into a second serial electric signal;and a second shift register, operatively connected to said receiver, forconverting the second serial electric signal delivered thereto by saidreceiver into a second parallel electric signal.